Traffic ancillary areas are those built-up or non built-up areas classified as road areas and yet which are not part of the carriageway (e.g. grassy areas in the middle of a roundabout).
For rail transport, traffic ancillary areas are built-up or non built-up areas adjacent to the track which serve rail transport.
For air transport, traffic ancillary areas are those areas of an airport or airfield lying outside the runways, the taxiways or aprons.
[Source: AdV (2008): GeoInfoDok, ATKIS-Objektartenkatalog Basis-DLM, Version 6.0]